In a gigabit Ethernet (GE)-passive optical network (PON), which is a type of a conventional time division multiplexing (TDM)-passive optical network (PON), a feeder fiber accepts the maximum 32 subscribers and provides a total bandwidth of 1 Gbps. A gigabit (G)-PON, which is another type of the conventional TDM-PON, is being developed, and accepts 64 subscribers and provides a total bandwidth of 2.6 Gbps downward and 1.2 Gbps upward. A transmission distance of the conventional TDM-PON is prescribed to 20 Km. It is expected that services requiring a high bandwidth, including an IPTV, will be in the mainstream within a few years, and accordingly, a fiber to the home (FTTH) optical network is being developed, and a GE-PON is currently provided. However, as the number of subscribers of the FTTH optical network increases, it is required to efficiently use an infrastructure of a conventional optical network. Also, the conventional optical network needs to be improved so as to provide an increased bandwidth to a subscriber.
A dense wavelength division multiplexing (WDM)-PON is widely known as a next generation optical network. The dense WDM-PON is being actively studied specifically in Korea, and a system having 1 Gbps per wavelength and 16 optical wavelength multiplexing structure is about to be commercialized. However, an optical transmission/reception module of the dense WDM-PON is much more expensive than that of the GE-PON, and thus it is not suitable to apply the dense WDM-PON to the FTTH optical network with a current price level. Also, in order to apply the dense WDM-PON, a remote node, and an optical terminal of a subscriber need to be exchanged. Accordingly, the WDM-PON is only applied to a few new subscribers who require a high bandwidth.